[dpdk-stable] patch 'eal: fix hang in control thread creation' has been queued to stable release 20.11.2

[Xueming Li]

Hi,

FYI, your patch has been queued to stable release 20.11.2

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 05/12/21. So please
shout if anyone has objections.

Also note that after the patch there's a diff of the upstream commit vs the
patch applied to the branch. This will indicate if there was any rebasing
needed to apply to the stable branch. If there were code changes for rebasing
(ie: not only metadata diffs), please double check that the rebase was
correctly done.

Queued patches are on a temporary branch at:
https://github.com/steevenlee/dpdk

This queued commit can be viewed at:
https://github.com/steevenlee/dpdk/commit/1324beafbae000e862df621c2378fa3b2631f98c

Thanks.

Xueming Li <xuemingl at nvidia.com>

---
>From 1324beafbae000e862df621c2378fa3b2631f98c Mon Sep 17 00:00:00 2001
From: Luc Pelletier <lucp.at.work at gmail.com>
Date: Wed, 7 Apr 2021 16:16:06 -0400
Subject: [PATCH] eal: fix hang in control thread creation
Cc: Luca Boccassi <bluca at debian.org>

[ upstream commit af68c1d699be6c369e296b775bdbf13ae18b79cc ]

The affinity of a control thread is set after it has been launched. If
setting the affinity fails, pthread_cancel is called followed by a call
to pthread_join, which can hang forever if the thread's start routine
doesn't call a pthread cancellation point.

This patch modifies the logic so that the control thread exits
gracefully if the affinity cannot be set successfully and removes the
call to pthread_cancel.

Fixes: 6383d2642b62 ("eal: set name when creating a control thread")

Signed-off-by: Luc Pelletier <lucp.at.work at gmail.com>
Acked-by: Olivier Matz <olivier.matz at 6wind.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
---
 lib/librte_eal/common/eal_common_thread.c | 29 +++++++++++++----------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/lib/librte_eal/common/eal_common_thread.c b/lib/librte_eal/common/eal_common_thread.c
index 3347e91bf2..03dbcd9e86 100644
--- a/lib/librte_eal/common/eal_common_thread.c
+++ b/lib/librte_eal/common/eal_common_thread.c
@@ -187,14 +187,18 @@ static void *ctrl_thread_init(void *arg)
 		eal_get_internal_configuration();
 	rte_cpuset_t *cpuset = &internal_conf->ctrl_cpuset;
 	struct rte_thread_ctrl_params *params = arg;
-	void *(*start_routine)(void *) = params->start_routine;
+	void *(*start_routine)(void *);
 	void *routine_arg = params->arg;
 
 	__rte_thread_init(rte_lcore_id(), cpuset);
 
 	pthread_barrier_wait(&params->configured);
+	start_routine = params->start_routine;
 	ctrl_params_free(params);
 
+	if (start_routine == NULL)
+		return NULL;
+
 	return start_routine(routine_arg);
 }
 
@@ -218,14 +222,12 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
 	params->refcnt = 2;
 
 	ret = pthread_barrier_init(&params->configured, NULL, 2);
-	if (ret != 0) {
-		free(params);
-		return -ret;
-	}
+	if (ret != 0)
+		goto fail_no_barrier;
 
 	ret = pthread_create(thread, attr, ctrl_thread_init, (void *)params);
 	if (ret != 0)
-		goto fail;
+		goto fail_with_barrier;
 
 	if (name != NULL) {
 		ret = rte_thread_setname(*thread, name);
@@ -236,19 +238,22 @@ rte_ctrl_thread_create(pthread_t *thread, const char *name,
 
 	ret = pthread_setaffinity_np(*thread, sizeof(*cpuset), cpuset);
 	if (ret != 0)
-		goto fail_cancel;
+		params->start_routine = NULL;
 
 	pthread_barrier_wait(&params->configured);
 	ctrl_params_free(params);
 
-	return 0;
+	if (ret != 0)
+		/* start_routine has been set to NULL above; */
+		/* ctrl thread will exit immediately */
+		pthread_join(*thread, NULL);
 
-fail_cancel:
-	pthread_cancel(*thread);
-	pthread_join(*thread, NULL);
+	return -ret;
 
-fail:
+fail_with_barrier:
 	pthread_barrier_destroy(&params->configured);
+
+fail_no_barrier:
 	free(params);
 
 	return -ret;
-- 
2.25.1

---
  Diff of the applied patch vs upstream commit (please double-check if non-empty:
---
--- -	2021-05-10 23:59:30.107955900 +0800
+++ 0137-eal-fix-hang-in-control-thread-creation.patch	2021-05-10 23:59:26.530000000 +0800
@@ -1 +1 @@
-From af68c1d699be6c369e296b775bdbf13ae18b79cc Mon Sep 17 00:00:00 2001
+From 1324beafbae000e862df621c2378fa3b2631f98c Mon Sep 17 00:00:00 2001
@@ -4,0 +5,3 @@
+Cc: Luca Boccassi <bluca at debian.org>
+
+[ upstream commit af68c1d699be6c369e296b775bdbf13ae18b79cc ]
@@ -16 +18,0 @@
-Cc: stable at dpdk.org